There is additional conversation going on about this issue on the Photoshop General Discussion forum on Adobe. This bug is a big pain and affecting workflow, but another workaround was mentioned that has worked for me. (Thank you, Ivor) and this might help in the meantime so I will pass it along. If you copy the transformed text into a brand new text box and work with it from there, the leading works and you can scrub with the arrow keys just fine afterwards without having to use the Properties window. I haven't tested it a million different ways, but it seems good so far for me. If you go to the forum mentioned, search for Photoshop CC 2018 line spacing and you should find the discussion.
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